Consider using different versions when new releases are made

[Sabryr]

I am assisting a user to use plink2 on our HPC cluster and your versioning course issues for us.

i.e. using the same version for different releases and distinguish them using a date in brackets.

Concerns this version http://s3.amazonaws.com/plink2-assets/plink2_linux_x86_64_20181028.zip) When using February version -bash-4.1$ plink2 --version PLINK v2.00a2LM 64-bit Intel (15 Feb 2018)

When using October version bash-4.1$ plink2 --version PLINK v2.00a2LM 64-bit Intel (28 Oct 2018)

[chrchang]

I was planning to start using real version numbers at the beginning of beta testing. (About 85% of the way there; still need merge and multiallelic-dosage functions before the program skeleton is complete.)

[Sabryr]

Thank you for the update.